In various types of lithography systems charged particles are used to pattern a substrate. Such charged particle lithography systems include electron and ion based lithography systems. In order to form an image, an electron-sensitive or ion-sensitive material such as photoresist is disposed on an outer surface of a substrate to intercept the respective electrons or ions. In direct write systems, a charged particle beam may be subject to random scan (vector scan) to write a pattern in serial fashion by scanning a charged particle beam into a photoresist or other target material. Other charged particle lithography systems provide a wide beam of charged particles that is divided into smaller beams or beamlets using a masking or patterning system in order to form an image in the photoresist. Generally, these latter systems produce a low emittance high brightness beam that illuminates the masking or patterning system. The image formed by dividing the wide beam into multiple beamlets is then projected onto a photoresist to define the pattern to be formed in the substrate.
Some charged particle lithography systems that generate multiple beamlets from a wider beam employ a fixed stencil mask in which a medium or membrane has a set of open regions defining a desired pattern through which charged particles are conducted toward the substrate. In other charged particle lithography systems, a programmable aperture plate that contains a set of regularly spaced holes may provide multiple different beamlets from the wide area beam. The programmable aperture plate system is also equipped with a multiplicity of control electrodes to switch an individual beamlet on or off depending on whether a desired portion of the substrate is to be illuminated or not.
For charged particle lithography systems that employ a fixed mask or programmable aperture plate system, most tools illuminate the fixed mask or programmable aperture plate system with a wide parallel beam. This beam typically originates from a small point source that produces a divergent beam. In order to focus the divergent beam to form a more parallel charged particle beam before patterning into smaller beamlets, a condenser lens system is provided upstream of the masking system. After passing through the fixed mask or programmable apertures the charged particle beam is then conducted through a projection optics system which may generate a desired image reduction to produce a desired pattern at the proper dimension on a substrate. One issue with such charged particle lithography systems is the complexity and size of the lithography system because of the necessity to generate a charged particle beam from a high brightness point source, to spread out the beam, and then collimate the beam before entering a mask. It is with respect to these and other considerations that the present improvements have been needed.